ABSTRACT The Methods Core provides expertise, leadership and infrastructure to promote and facilitate the quality of HIV research conducted by CHIPTS researchers and collaborators, both domestically and globally. The Methods Core has a history of venturing to the cutting edge of research methodology and technology to offer the HIV research community new platforms and tools to optimize the potential of their research. This includes integrating mobile phone-based assessment, biomarker data, and other measurement techniques into study designs that maintain scientific rigor while adapting to the evolving environment of HIV prevention research. Consistent with OAR's NIH HIV/AIDS funding priorities, the Methods Core will provide services to guide research linked to HIV, with specific focus on comorbidities of substance use and mental health disorders that interfere with consistent viral suppression in HIV-positive individuals and in sustaining optimal prophylaxis for high-risk individuals. The Methods Core recognizes the paradigm shift required beyond traditional analytic approaches to incorporate advanced analytical approaches, and to broaden involvement across different disciplines, such as medicine, HIV, mental health and drug abuse research fields. As well, the interplay of technology and implementation science requires method development to advise HIV intervention delivery in real-world settings. Its three specific aims are: (1) SCIENCE: To foster cutting edge research by developing and disseminating innovative technologies and analytic strategies (e.g., modern measurement tools and multivariate statistical techniques) to HIV treatment and prevention research; (2) NETWORKING: To connect scientists across disciplines and with community partners to understand the available analytic methodologies and linking scientists to partners with complementary expertise; and (3) CAPACITY BUILDING: To recruit, mentor, retain high caliber investigators with methods expertise and to disseminate innovative methods, tools, and platforms through seminars and webinars. The Methods Core is a backbone for both CHIPTS scientists and community partners and prioritizes three overlapping areas of focus when providing services: measurement, statistical methods and multivariate models, and implementation science. The Methods Core is led by Director Li Li, PhD, Co-Director W Scott Comulada, DrPH, and Associate Director Sung Jae-Lee, PhD. The types of services provided include consultations on research design, power and sample-size calculations, data analysis, data management, grant proposal development, preparation of research findings for publication, training workshops and seminars and selection of appropriate models, including analysis of multiple biomedical and behavioral HIV end points. Epidemiological and biostatistical expertise within a broader causal-inference paradigm have always been central to guiding services provided by the Methods Core.